Packaged piezoelectric oscillator incorporating capacitors and method of making the same

ABSTRACT

A packaged piezoelectric oscillator is provided which comprises an insulating package body, a piezoelectric element, and a lid member. The package body has an upwardly open housing groove which has a bottom surface formed with oscillator electrodes at both ends of the housing groove. The package body is externally formed with first to third electrodes spaced from each other. The first and second electrodes extend into the housing groove for electrical connection to the respective oscillator electrodes, whereas the third electrode is located between the first and second electrodes. The piezoelectric element is fixedly received in the housing groove of the insulating package body and held in electrical conduction with the respective oscillator electrodes. The lid member is attached to the package body to close the housing groove. The lid member has a lower surface formed with first to third capacitor electrodes in electrical conduction with the first to third lead electrodes, respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a packaged piezoelectric oscillator of thetype which itself incorporates a pair of capacitors. The presentinvention also relates to a method of making a plurality of suchoscillators at a time.

2. Description of the Related Art:

A packaged piezoelectric oscillator incorporating a pair of capacitorsis conventional. For better understanding, a typical example of such anoscillator is illustrated in FIGS. 45 and 46 of the accompanyingdrawings.

As shown in FIGS. 45 and 46, specifically, the prior art packagedpiezoelectric oscillator 4 comprises a piezoelectric element 1 enclosedin an insulating package which consists of an elongate base plate 5 anda cover member CM. The piezoelectric element 1 includes a ceramic bar1a, a lower electrode film 1b formed on the lower surface of the ceramicbar 1a, and an upper electrode film 1c formed on the upper surface ofthe ceramic bar 1a. The respective electrode films 1b, 1c may be made ofsilver by sputtering for example. The respective electrode films overlapeach other longitudinally of the ceramic bar 1a over a predeterminedarea, and this overlapping area plays an important role in determiningthe characteristics of the piezoelectric element 1.

The base plate 5 is made of a dielectric substance. The base plate 5 isformed with first to third lead electrodes 6, 7, 8 spaced from eachother longitudinally of the base plate. The first and second leadelectrodes 6, 7 are held in electrical conduction with the respectiveelectrode films 1b, 1c of the piezoelectric element 1 by deposits 9 ofelectrically conductive adhesive, so that the first and second leadelectrodes 6, 7 are utilized to supply electric power for piezoelectricoscillation. Further, due to the dielectric nature of the base plate 5,two capacitors 3 are provided respectively between the first and thirdlead electrodes 6, 8, and between the second and third lead electrodes7, 8.

For mounting on a circuit board (not shown), the above-describedpiezoelectric oscillator 4 is generally arranged in parallel to a CMOSinverter 2 (CMOS: complementary metal oxide semiconductor), as shown inFIG. 27. Further, the first and second lead electrodes 6, 7 of thepiezoelectric element 1 are grounded through the respective capacitors 3which work for phase inversion.

According to the prior art described above, since the piezoelectricoscillator 4 itself incorporates the capacitors 3, it is possible torealize a compact circuit arrangement in comparison with separatelyproviding capacitors. Further, the prior art packaged piezoelectricoscillator 4 is also advantageous in that the user need not care aboutthe capacitance of the capacitors 3 which is selected by the supplier.

However, the prior art piezoelectric oscillator is still disadvantageousin the following respects.

First, since the respective lead electrodes 6, 7, 8 for the capacitors 3are directly exposed to the circuit board to which the piezoelectricoscillator 4 is mounted, the dielectric constant of the base plate 5 maybe likely to vary under the influences of nearby conductor parts on thecircuit board such as wirings and/or solder deposits. As a result, thecapacitance of the capacitors may vary to result in fluctuation of theoscillation characteristics of the piezoelectric oscillator 4.

Secondly, since the base plate 5 works dually as a capacitor body and asa member for forming the respective lead electrodes 6, 7, 8, there is alimitation in optionally selecting the capacitance of the respectivecapacitors 3.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide apackaged piezoelectric oscillator which is capable of overcoming theabove described problems of the prior art.

Another object of the present invention is to provide a method of makinga plurality of packaged piezoelectric oscillators at one time at a lowcost.

According to one aspect of the present invention, there is provided apackaged piezoelectric oscillator comprising: an insulating package bodyhaving an upwardly open housing groove which has a bottom surface formedwith oscillator electrodes at both ends of the housing groove, thepackage body being externally formed with first to third electrodesspaced from each other, the first and second electrodes extending intothe housing groove for electrical connection to the respectiveoscillator electrodes, the third electrode being located between thefirst and second electrodes; a piezoelectric element fixedly received inthe housing groove of the insulating package body and held in electricalconduction with the respective oscillator electrodes; and a lid memberattached to the package body to close the housing groove, the lid memberhaving a lower surface formed with first to third capacitor electrodesin electrical conduction with the first to third lead electrodes,respectively.

With the arrangement described above, the lid member carrying thecapacitor electrodes can be reasonably spaced from the circuit board towhich the piezoelectric oscillator is mounted. Thus, it is possible toreduce the possibility of the capacitors (provided by the combination ofthe lid member and the capacitor electrodes) from being adverselyinfluenced by nearby conductor parts on the circuit board. Further,since the lid member is separate from the package body, there will bemuch freedom in selecting the dimensions for the capacitor electrodes,thereby making it possible to adjust the capacitance of the capacitorsin a relatively wide range.

According to an embodiment of the present invention, the housing groovehas an intermediate wider width portion, and each end of the housinggroove is provided with a pair of end positioning walls projectingtoward each other for providing a narrower width portion between thepair of end positioning walls. The end positioning walls are effectivefor preventing the piezoelectric element from deviating sidewise.Preferably, the pair of end positioning walls may be inclined so thatthe narrower width portion at said each end of the housing groove tapersdownward. In the latter case, the piezoelectric element is guided by theinclined positioning walls to an optimum position.

The piezoelectric element may be fixed to the oscillator electrodeswithin the housing groove by deposits of a relatively soft electricallyconductive adhesive. The soft adhesive deposits provide a bufferingeffect against thermal stresses and strains.

The lid member may have an upper surface formed entirely with anelectrically insulating layer. In this case, it is preferable that theinsulating layer differs in color from the lid member and is formed withat least one indication cutout. Further, it is also advantageous if theinsulating layer is nearly equal in coefficient of thermal expansion tothe lid member, thereby preventing thermal bending due to a differencein thermal expansion between the insulating layer and the lid member.

Alternatively, the lid member may have an conductor insert layerembedded therein.

The lid member may be attached to the package body by a bonding layerwhich includes conductive portions at positions corresponding to therespective lead electrodes, and nonconductive portions at positionsclear of the lead electrodes. The conductive portions of the bondinglayer may be made of a electrically conductive resin or a solder paste,whereas the non-conductive portions may be made of a thermoplastic resinadhesive.

Alternatively, the bonding layer may be entirely made of an anisotropicpressure sensitive conductive elastomer, in which case the bonding layeris rendered electrically conductive by predetermined compression only atthe conductive portions. The details of the anisotropic pressuresensitive conductive elastomer will be described hereinafter.

The package body may comprise a plurality of electrode forming portionsmade of a metal-platable resin, and a plurality of non-electrode formingportions arranged alternately with the electrode forming portions andmade of a non-platable resin. In this case, the lead electrodes and theoscillator electrodes are selectively formed only on the electrodeforming portions of the package body even if the package body as a wholeis subjected to plating with a metal.

According to another aspect of the present invention, there is provideda method of making packaged piezoelectric oscillators comprising thesteps of: preparing a resinous master package plate formed with aplurality of upwardly open housing grooves, each of the housing groovesbeing flanked by first to third pairs of through-holes penetrating themaster package plate, the first and second pairs of through-holes beinglocated at positions corresponding to both ends of said each housinggroove, the third pair of through-holes being located between the firstand second pairs of through-holes; forming first to third leadelectrodes extending on upper and lower surfaces of the master packageplate transversely of said each housing groove respectively at the firstto third pairs of through-holes, the first to third lead electrodesfurther extending respectively within the first to third pairs ofthrough-holes, the first and second lead electrodes further extendinginto said each housing groove; forming oscillator electrodes on a bottomsurface of said each housing groove respectively at both ends thereof inelectrical conduction with the first and second lead electrodes;mounting a piezoelectric element in said each housing groove inelectrical conduction with the respective oscillator electrodes;preparing a master lid plate having a lower surface formed with first tothird capacitor electrodes in corresponding relation to the first tothird lead electrodes for said each housing groove; attaching the masterlid plate to the master package plate to bring the first to thirdcapacitor electrodes into electrical conduction with the first to thirdlead electrodes; and cutting the master package plate together with theattached master lid plate to provide a plurality of packagedpiezoelectric oscillators.

The preparation of the master package plate may comprise a primarymolding step of forming a plurality of electrode forming portions madeof a metal-platable resin and spaced from each other, and a secondarymolding step of forming a plurality of non-electrode forming portionsmade of a non-platable resin and arranged alternately with the electrodeforming portions. Alternatively, the preparation of the master packageplate may comprise a primary molding step of forming a plurality ofnonelectrode forming portions made of a non-platable resin and spacedfrom each other, and a secondary molding step of forming a plurality ofelectrode forming portions made of a metal-platable resin and arrangedalternately with the electrode forming portions.

Other objects, features and advantages of the present invention will befully understood from the following detailed description given withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a view, in longitudinal section, showing a packagedpiezoelectric oscillator according to a first embodiment of the presentinvention;

FIG. 2 is a sectional view taken on lines II--II in FIG. 1;

FIG. 3 is a sectional view taken on lines III--III in FIG. 1;

FIG. 4 is a sectional view taken on lines IV--IV in FIG. 1;

FIG. 5 is a plan view showing a package body of the same oscillator asseen in the direction of arrows V--V in FIG.

FIG. 6 is a perspective view showing the same oscillator in an explodedstate;

FIG. 7 is an exploded perspective similar to FIG. 6 but showing apackaged piezoelectric oscillator according to a second embodiment ofthe present invention;

FIG. 8 is a sectional view taken along on lines VIII--VIII in FIG. 7;

FIG. 9 is an exploded perspective again similar to FIG. 6 but showing apackaged piezoelectric oscillator according to a third embodiment of thepresent invention;

FIG. 10 is a perspective view showing a lid member incorporated in theoscillator of the third embodiment;

FIG. 11 is a perspective view showing a master package plate which isused for making a plurality of packaged piezoelectric oscillators at atime;

FIG. 12 is a sectional view taken along lines XII--XII in FIG. 11;

FIG. 13 is a sectional view taken along lines XIII--XIII in FIG. 11;

FIG. 14 is a perspective view similar to FIG. 11 but showing the samemaster package plate after forming conductor coatings at respectivethrough-holes;

FIG. 15 is a sectional view taken along lines XV--XV in FIG. 14;

FIG. 16 is a perspective view showing the master package plate of FIG.11 after forming conductor strips on the tail surface of the masterpackage plate;

FIG. 17 is a sectional view taken along lines XVII--XVII in FIG. 16;

FIG. 18 is a perspective view showing the master package plate of FIG.11 after forming conductor strips on the head surface of the masterpackage plate;

FIG. 19 is a sectional view taken along lines XIX--XIX in FIG. 18;

FIG. 20 is an exploded perspective view showing the master package plateof FIG. 11 together with loaded piezoelectric elements and a master lidplate;

FIG. 21 is a sectional view taken along lines XXI--XXI in FIG. 20;

FIG. 22 is a perspective view showing the assembly of the master packageplate and the master lid plate at the time of cutting into a pluralityof packaged piezoelectric oscillators;

FIG. 23 is a perspective view showing one of the oscillators obtained asa result of cutting;

FIG. 22 is a view, in longitudinal section, showing a packagedpiezoelectric oscillator according to a fourth embodiment of the presentinvention;

FIG. 25 is a sectional view taken along lines XXV--XXV in FIG. 24;

FIG. 26 is a sectional view taken along lines XXVI--XXVI in FIG. 24;

FIG. 27 is a sectional view taken along lines XXVII--XXVII in FIG. 24;

FIG. 28 is a plan view showing a package body of the same oscillator asseen in the direction of arrows XXVIII--XXVIII in FIG. 24;

FIG. 29 is a perspective view showing an intermediate package frameobtained by primary molding and used for making a complete package bodyto be incorporated in the oscillator of the fourth embodiment;

FIG. 30 is a sectional view taken along lines XXX--XXX in FIG. 29;

FIG. 31 is a plan view showing the intermediate package frame of FIG.29;

FIG. 32 is a perspective view showing the complete package body obtainedby secondary molding;

FIG. 33 is a sectional view taken along lines XXXIII--XXXIII in FIG. 32;

FIG. 34 is a plan view showing the complete package body of FIG. 32;

FIG. 35 is a perspective view showing another intermediate package frameobtained by primary molding and used for making another complete packagebody to be incorporated in the oscillator of the fourth embodiment;

FIG. 36 is a perspective view showing the complete package body obtainedby secondary molding;

FIG. 37 is a perspective view showing an intermediate master packageframe obtained by primary molding and used for making a plurality ofcomplete package bodies;

FIG. 38 is a sectional view taken along lines XXXVIII--XXXVIII in FIG.37;

FIG. 39 is a perspective view showing a complete master package plateobtained by secondary molding;

FIG. 40 is a sectional view taken along lines XXXX--XXXX in FIG. 39;

FIG. 41 is a perspective view showing another intermediate masterpackage frame obtained by primary molding and used for making aplurality of complete package bodies;

FIG. 42 is a sectional view taken along lines XXXXII--XXXXII in FIG. 41;

FIG. 43 is a perspective view showing another complete master packageplate obtained by secondary molding;

FIG. 42 is a sectional view taken along lines XXXXIV--XXXXIV in FIG. 43;

FIG. 45 is a front view showing a prior art packaged piezoelectricoscillator;

FIG. 46 is a plan view showing the same prior art oscillator; and

FIG. 47 is a diagram showing a circuit incorporating the oscillator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 to 6 of the accompanying drawings, there isshown a packaged piezoelectric oscillator according to a firstembodiment of the present invention. The oscillator mainly comprises apackage body 11, a piezoelectric element 13, and a lid member 16.

The package body it is a rectangular block which is made of aninsulating material such as epoxy resin. The package body 11 has anupwardly open housing groove 12. The bottom surface of the groove 12 isformed with film-like oscillator electrodes 14, 15 respectively at bothends of the groove 12.

The package body 11 is further formed with three film-like leadelectrodes which are spaced from each other longitudinally of thepackage body 11 and include a pair of end lead electrodes 17, 18 (firstand second lead electrodes) and an intermediate lead electrode 19 (thirdlead electrode). Each of the end lead electrodes 17, 18 is electricallyconnected to a corresponding one of the oscillator electrodes 14, 15 atthe bottom of the package body 11, and comprises an external bottom filmportion 17a, 18a, a pair of external side film portions 17b, 18b, a pairof external top film portions 17c, 18c, and a pair of internal side filmportions 17d, 18d. The intermediate lead electrode 19 comprises anexternal bottom film portion 19a, a pair of external side film portions19b, and a pair of external top film portions 19c.

The piezoelectric element 13 is accommodated in the housing groove 12 ofthe package body 11. The piezoelectric element 13 comprises a ceramicbar 13a, a lower electrode film 13b formed on the bottom face of theceramic bar 13a to extend onto one end face of the bar, and an upperelectrode film 13c formed on the ceramic bar 13a to extend onto theother end face of the bar. The lower electrode film 13b is electricallyconnected to the oscillator electrode 14 by a deposit 20 of electricallyconductive adhesive, whereas the upper electrode film 13c iselectrically connected to the other oscillator electrode 15 by anotherdeposit 21 of electrically conductive adhesive. Apparently, thepiezoelectric element 13 is fixed in place within the housing groove 12by the respective adhesive deposits 20, 21.

Preferably, the electrically conductive adhesive deposits 20, 21 may bemade of a relatively soft resin such as thermoplastic resin or siliconeresin. In this case, the flexibility or elasticity of the soft resinabsorbs or buffers a difference in thermal expansion between the packagebody 11 and the piezoelectric element 13, so that the adhesive deposits20, 21 can be reliably prevented from undergoing crack formation underthermal loads.

Each end of the housing groove 12 of the package body 11 is integrallyprovided with a pair of end positioning walls 12a protruding toward eachother for reducing the width at the relevant end of the housing groove12 in comparison with the normal groove width W (see FIG. 5). The pairof end positioning walls 12a prevents the piezoelectric element 13 fromtranslationally or angularly deviating sidewise within the housinggroove 12. The internal side film portions 17d, 18d of each of the endlead electrodes 17, 18 are formed on the respective end positioningwalls 12a.

The lid member 16 is a rectangular plate which is made of a dielectricsubstance such as barium titanate. The underside of the lid member 16 isformed with three film-like capacitor electrodes 16a, 16b, 16c (first tothird capacitor electrodes) which are spaced from each otherlongitudinally of the lid member. Due to combinations of these capacitorelectrodes, the lid member 16 is made to have two capacitors.

The lid member 16 is fixed on the package body 11 by means of a suitablebonding layer 22 to close the housing groove 12. The bonding layer 22may comprise non-conductive portions at positions clear of therespective capacitor electrodes 16a, 16b, 16c, and conductive portionsat positions corresponding to the capacitor electrodes 16a, 16b, 16cwhich are thereby held in electrical conduction with the lead electrodes17, 18, 19, respectively, of the package body 11. The conductiveportions of the bonding layer 22 may be made of a conductive adhesive ora solder paste, whereas the non-conductive portions may be made of arelatively soft resin such as thermoplastic resin. The use of the softresin for the non-conductive portions of the bonding layer 22 isadvantageous in that the soft resin absorbs or buffers a difference inthermal expansion between the package body 11 and the lid member 16, sothat the bonding layer 22 is prevented from breaking under thermalloads.

Alternatively, the bonding layer 22 may be uniformly made of ananisotropic pressure sensitive conductive elastomer which is a compositematerial consisting of a silicone rubber matrix and metal particlesdispersed in the matrix. Specifically, the metal particles in the rubbermatrix are densely dispersed in a first direction but sparsely dispersedin a second direction perpendicular to the first direction. Thus, theanisotropic conductive elastomer becomes conductive when compressed inthe first direction to a degree higher than a predetermined level, butremains non-conductive when compressed in the second direction.

In the illustrated embodiment, due to the thickness of the capacitorelectrodes 16a, 16b, 16c and the lead electrodes 17, 18, 19, the bondinglayer 22 made uniformly of anisotropic pressure sensitive conductiveelastomer is compressed to a higher degree at the respective capacitorelectrodes 16a, 16b, 16c than at other positions when the lid member 16is attached to the package body 11. Therefore, the bonding layer 22becomes conductive selectively only at the capacitor electrodes 16a,16b, 16c. Apparently, the use of the anisotropic pressure sensitiveconductive elastomer is advantageous for facilitating the step ofattaching the lid member 16 to the package body 11.

The top surface of the lid member 16 is entirely covered by anelectrically insulating layer 23. This insulating layer may be formed byapplying an insulating paste by a thick film printing method, andthereafter drying the paste for setting. The insulating layer 23 may bealso formed by spraying an insulating paint, and thereafter drying thepaint for curing.

Alternatively, the insulating layer 23 may be formed by depositing ametal oxide (e.g. Al₂ O₃, SiO₂, or MgO) by a vacuum deposition method.Preferably, the insulating layer 23 has nearly the same coefficient ofthermal expansion as the lid member 16 because otherwise the lid member16 combined with the insulating layer 23 may longitudinally bend underthermal loads due to the so-called bimetal phenomenon.

When the piezoelectric oscillator is mounted on a printed circuit board24 (see FIG. 1), an external conductive component (not shown) on thesame circuit board 22 may come in contact with or close proximity to thelid member 16 of the oscillator. In such a case, however, the insulatinglayer 23 prevents the lid member 16 from being electrostaticallyinfluenced by the external component. As a result, the oscillationfrequency of the piezoelectric oscillator is prevented from fluctuating.

As shown in FIG. 6, the insulating layer 23 may be preferably formedwith indication cutouts 23a, 23b at positions between the respectivecapacitor electrodes 16a, 16b, 16c. In this case, the color of theinsulating layer 23 should advantageously be different from that of thelid member 16 for highlighting the indication cutouts 23a, 23b.

FIGS. 7 and 8 show a packaged piezoelectric oscillator according to asecond embodiment of the present invention. The oscillator of the secondembodiment is similar to that of the first embodiment but differstherefrom only in that each end of the housing groove 12 of the packagebody 11 is integrally provided with a pair of end positioning walls 12Awhich are inclined downwardly toward each other. Apparently, the pair ofinclined end positioning walls 12A facilitates insertion of thepiezoelectric element 13 into the housing groove 12 while also providingautomatic longitudinal alignment of the element 13 relative to thegroove 12.

FIGS. 9 and 10 show a packaged piezoelectric oscillator according to athird embodiment of the present invention. The oscillator of the thirdembodiment is similar to that of the second embodiment but differstherefrom only in that the lid member 16 is provided with anelectrically conductive film 23' embedded therein as an insert. Theprovision of such an insert prevents the lid member 16 from beingelectrostatically influenced by an external conductive component (notshown), thereby preventing the oscillation frequency of the lid member16 from fluctuating. Apparently, the conductive film 23' may be providedin place of or in addition to the insulating layer 23 (see FIGS. 1-6) ofthe first embodiment.

As shown in FIG. 10, the lid member 16 of the third embodiment may bemade in the following manner. First, a metal paste such as palladiumpaste is applied in a layer or film 23' on a first ceramic green sheet16'. Then, a second ceramic green sheet 16" is laminated on the pastelayer 23'. Finally, the laminate thus obtained is compressed in thedirection of lamination and subjected to baking for setting the pastelayer 23'.

The packaged piezoelectric oscillator according to any one of theforegoing embodiments may be manufactured substantially by a similarmethod. Now, such a manufacturing method is specifically described withreference to FIGS. 11 through 23 of the accompanying drawings.

First, as shown in FIGS. 11 through 13, a master package plate A made ofa synthetic resin (insulating material) is prepared to have a pluralityof housing grooves 12 in plural rows. Therefore, the master packageplate A can provide a plurality of unit package bodies 11 whensubsequently divided along longitudinal and transverse cutting lines E1,E2. Further, the master package plate A is also formed with a pluralityof through-holes B suitably spaced along the respective longitudinalcutting lines E1 and arranged in transverse rows parallel to thetransverse cutting lines E2. It should be appreciated that each end ofeach housing groove 12 is actually formed with a pair of end positioningportions 12a (see FIG. 6), but they are omitted in FIGS. 11-13 only forsimplicity of illustration.

Then, as shown in FIGS. 14 and 15, conductor coatings 17b, 18b, 19b areformed in the respective through-holes B by loading a metal paste (e.g.silver paste) therein for example. Apparently, these conductor coatingslater provide the external side film portions 17b, 18b, 19b of therespective lead electrodes 17, 18, 19 (see FIG. 6).

Then, as shown in FIGS. 16 and 17, conductor strips 17a, 18a, 19a areformed on the tail surface of the master package plate A by applying ametal paste (e.g. silver paste) in parallel to the transverse cuttinglines E2 along the respective transverse rows of through-holes B.Apparently, these conductor strips later provide the external bottomfilm portions 17a, 18a, 19a of the respective lead electrodes 17, 18, 19(see FIGS. 1-3).

Then, as shown in FIGS. 18 and 19, conductor coatings 17c, 18c, 19c areformed on the head surface of the master package plate A at therespective through-holes B by applying a metal paste (e.g. siliverpaste) in parallel to the transverse cutting lines E2 along therespective transverse rows of through-holes B. Apparently, theseconductor strips later provide the external top film portions 17c, 18c,19c of the respective lead electrodes 17, 18, 19 (see FIG. 6).

As also shown in FIGS. 18 and 19, conductor coatings 14, 15, 17d, 18dare also formed in the respective housing grooves 12 by applying a metalpaste (e.g. silver paste). Apparently, these conductor coatingscorrespond to the internal side film portions 17d, 18d of the respectiveend lead electrodes 17, 18 and the oscillator electrodes 12, 15. Itshould be appreciated that the formation of the internal side filmportions 17d, 18d and oscillator electrodes 14, 15 may be performedeither simultaneously with or separately from the formation of theexternal top film portions 17c, 18c, 19c.

The process steps shown in FIGS. 14 through 19 for forming the leadelectrodes 17, 18, 19 and the oscillator electrodes 14, 15 may beperformed in any sequence, and selected ones of these process steps maybe performed simultaneously. For instance, the formation of the bottomfilm portions 17a, 18a, 19a of the respective lead electrodes 17, 18, 19may be performed before forming the external side film portions 17b,18b, 19b.

As an alternative to applying a metal paste (e.g. silver paste), thelead electrodes 17, 18, 19 and the oscillator electrodes 14, 15 may beformed by a combination of metal plating and subsequent patterning.Specifically, the master package plate A as a whole is first coated witha metal by electroless plating or electrolytic plating, and the metalcoating or plating is then patterned by photoetching or laser trimminginto the lead electrodes 17, 18, 19 and the oscillator electrodes 16,15. For this purpose, the master package plate A need be entirely madeof a metal-platable resin. The term "metal-platable resin" is usedherein to mean that the resin can be plated with a metal. Such a resinmay be prepared by mixing a suitable amount of metal catalyst such aspalladium or gold in a resin matrix consisting of liquid crystal polymer(LCP), polyether sulfone (PES) or polyphenylene sulfide (PES).

Then, as shown in FIGS. 20 and 21, a plurality of piezoelectric elements13 are placed in the respective housing grooves 12 and fixed therein bydeposits 20, 21 of an electrically conductive adhesive. As previouslydescribed, each element 13 is held in electrical connection with therespective oscillator electrodes 12, 15 through the conductive adhesivedeposits 20, 21.

Then, as also shown in FIG. 20, a master lid plate C made of adielectric substance is prepared which provides a plurality of unit lidmembers 16 when subsequently divided along the longitudinal andtransverse cutting lines E1, E2. The underside of the master lid plate Cis formed with a plurality of electrodes strips 16a, 16b, 16c extendingin parallel to the transverse cutting lines E2 in corresponding relationto the transverse rows of the through-holes B of the master packageplate A. The electrode strips 16a, 16b, 16c may be made by printing ametal paste or by vacuum deposition of a metal. Apparently, theseelectrodes strips correspond to the capacitor electrodes 16a, 16b, 16cof the respective unit lid members 16.

For attaching the master lid plate C to the master package plate A, abonding layer 22 is formed on the top surface of the master packageplate A, as shown in FIG. 21. As previously described, the bonding layer22 comprises non-conductive portions 22a at positions clear of therespective lead electrodes 17, 18, 19 of the master package plate A, andconductive portions 22b at positions corresponding to the leadelectrodes 17, 18, 19. The conductive portions 22b of the bonding layer22 may be made of a conductive adhesive or a solder paste, whereas thenon-conductive portions may be made of a thermoplastic resin. The masterlid plate C is pressed against the bonding layer 22 which is cured byheating.

As also described previously, the entirety of the bonding layer 22 maybe alternatively made of an anisotropic pressure sensitive conductiveelastomer. In this case, the bonding layer 22, which is initiallynon-conductive as a whole, becomes conductive only at the portions 22bwhere a higher compression is applied due to the presence of theelectrodes 16a, 16b, 16c, 17, 18, 19 when the master lid plate C ispressed against the master package plate A. Apparently, the use of theanisotropic pressure sensitive conductive elastomer is advantageous forfacilitating the step of attaching the master lid plate C to the masterpackage plate A.

Finally, as shown in FIG. 22, the assembly of the master package plate Aand the master lid plate C is cut by a highspeed rotary cutter D alongthe longitudinal and transverse cutting lines E1, E2 to provide aplurality of packaged piezoelectric oscillators BO. FIG. 23 shows one ofthe thus obtained oscillators 30.

FIGS. 24 through 28 show a packaged piezoelectric oscillator accordingto a fourth embodiment of the present invention. The oscillator of thisembodiment mainly comprises a package body 11', a piezoelectric element13, and a lid member 16. As can be readily appreciated, thepiezoelectric element 13 and lid member 16 of the fourth embodiment aresubstantially the same as those of the first embodiment, so that thedetails of these elements are not described.

The package body 11' is a rectangular block having an upwardly openhousing groove 12'. The bottom surface of the groove 12' is formed withfilm-like oscillator electrodes 14', 5' respectively at both ends of thegroove 12'.

The package body 11' is further formed with three film-like leadelectrodes which are spaced from each other longitudinally of thepackage body 11' and include a pair of end lead electrodes 17', 18' andan intermediate lead electrode 19'. Each of the end lead electrodes 17',18' is electrically connected to a corresponding one of the oscillatorelectrodes 14', 15' at the bottom of the package body 11', and comprisesan external bottom film portion 17a', 18a', a pair of external side filmportions 17b', 18b', a pair of external top film portions 17c', 18c',and a pair of internal side film portions 17d', 18d'. The intermediatelead electrode 19' comprises an external bottom film portion 19a', apair of external side film portions 19b', and a pair of external topfilm portions 19c'.

According to the fourth embodiment, the package body 11' consists of aplurality of electrode forming portions 11a', 11b', 11c' correspondingto the respective lead electrodes 17', 18', 19', and a plurality ofnon-electrode forming portions 11d', 11e', 11f', 11g' alternate with theelectrode forming portions 11a', 11b', 11c'. The electrode formingportions 11a', 11b', 11c' are made of a platable resin which may beprepared by mixing a suitable amount of metal catalyst such as palladiumor gold in a resin matrix consisting of liquid crystal polymer (LCP),polyether sulfone (PES) or polyphenylene sulfide (PES). On the otherhand, the non-electrode forming portions 11d', 11e', 11f', 11g' may bemade of a non-platable resin (e.g. LCP, PES or PES not containing metalcatalyst). As a result, the respective lead electrodes 17', 18', 19' canbe formed selectively only at the electrode forming portions 11a', 11b',11c' even if the package body 11' as a whole is subjected to electrolessor electrolytic plating.

The package body 11' having the above-described structure may be made bytwo different methods, as described below.

A first method is shown in FIGS. 29-34. According to this method, theplurality of non-electrode forming portions 11d', 11e', 11f', 11g',which are connected together by a plurality of connector rod portions11h', 11i', 11j', are first formed of a non-platable resin by primarymolding (FIGS. 29-31). Then, the plurality of electrode forming portions11a', 11b', 11c' are formed of a platable resin by secondary molding tobe alternate with the non-electrode forming portions 11d', 11e', 11f',11g' (FIGS. 32-34).

A second method is shown in FIGS. 35 and 36. According to this method,the plurality of electrode forming portions 11a', 11b', 11c', which areconnected together by a plurality of connector rod portions 11k', 11m',are first formed of a platable resin by primary molding (FIGS. 35).Then, the plurality of non-electrode forming portions 11d', 11e', 11f',11g' are formed of a non-platable resin by secondary molding to bealternate with the electrode forming portions 11a', 11b', 11c' (FIG.36).

Apparently, the provision of the electrode forming portions 11a', 11b',11c together with the non-electrode forming portions 11d', 11e', 11f',11kg' facilitates formation of the respective lead electrodes 17', 18',19' and the oscillator electrodes 14, 15.

For quantity production, a plurality of non-electrode forming barsA1'-A7', which are connected together by a plurality of connector rodportions A8', are first formed of a non-platable resin by a primarymolding, as shown in FIGS. 37 and 38. The primary molding is followed bysecondary molding for forming a plurality of electrode forming barsA9'-A14' by injecting a platable resin, as shown in FIGS. 39 and 40.

As a result of the primary and second molding operations describedabove, a master package plate A' is prepared which has a plurality ofhousing grooves 12' in plural rows. The master package plate A' canprovide a plurality of unit package bodies 11' when subsequently dividedalong longitudinal and transverse cutting lines E1, E2. Further, themaster package plate A' is also formed with a plurality of through-holesB' suitably spaced along the respective longitudinal cutting lines E1and arranged in transverse rows parallel to the transverse cutting linesE2.

Then, the master package plate A' as a whole is subjected to electrolessor electrolytic plating for forming lead electrodes 17', 18', 19' andoscillator electrodes 12', 15' (see FIGS. 24-28) only at the electrodeforming bars A9'-A14' which carry the through-holes B'. A plurality ofpackaged piezoelectric oscillators are produced by performing thesubsequent process steps which are similar to those (FIGS. 20-23) forthe first embodiment.

Alternatively, a plurality of electrode forming bars A9"-A14", which areconnected together by a plurality of connector rod portions A15", arefirst formed of a platable resin by a primary molding, as shown in FIGS.21 and 22. The primary molding is followed by secondary molding forforming a plurality of non-electrode forming bars A1"-A7" by injecting aplatable resin, thereby providing a master package plate A", as shown inFIGS. 43 and 44. The master package plate A" is subjected to subsequentprocess steps (as already described) for providing a plurality ofpackaged piezoelectric oscillators.

The preferred embodiments of the present invention being thus described,it is obvious that the same may be varied in many ways. Such variationsare not to be regarded as a departure from the spirit and scope of thepresent invention, and all such modifications as would be obvious tothose skilled in the art are intended to be included within the scope ofthe following claims.

We claim:
 1. A packaged piezoelectric oscillator comprising:aninsulating package body having a bottom mounting face and an upwardlyopen housing groove which has a bottom surface formed with oscillatorelectrodes at both ends of the housing groove, the package body beingexternally formed with first to third lead electrodes spaced from eachother, the first and second lead electrodes extending into the housinggroove for electrical connection to the respective oscillatorelectrodes, the third lead electrode being located between the first andsecond lead electrodes; a piezoelectric element fixedly received in thehousing groove of the insulating package body and held in electricallyconduction with the respective oscillator electrodes; and a lid memberupwardly spaced from the bottom mounting surface of the package body andattached to the package body to close the housing groove, the lid memberhaving a lower inside surface formed with first to third capacitorelectrodes in electrical conduction with the first to third leadelectrodes, respectively, none of the first to third capacitorelectrodes extending onto an upper outside surface of the lid member. 2.The oscillator according to claim 1, wherein the housing groove has anintermediate wider width portion, each end of the housing groove beingprovided with a pair of end positioning walls projecting toward eachother for providing a narrower width portion between the pair of endpositioning walls.
 3. The oscillator according to claim 2, wherein thepair of end positioning walls are inclined so that the narrower widthportion at said each end of the housing groove tapers downward.
 4. Theoscillator according to claim 1 , wherein the piezoelectric element isfixed to the oscillator electrodes within the housing groove by depositsof a relatively soft electrically conductive adhesive.
 5. The oscillatoraccording to claim 1, wherein the lid member has an upper surface formedentirely with an electrically insulating layer.
 6. The oscillatoraccording to claim 5, wherein the insulating layer differs in color fromthe lid member, the insulating layer being formed with at least oneindication cutout.
 7. The oscillator according to claim 5, wherein theinsulating layer is nearly equal in coefficient of thermal expansion tothe lid member.
 8. The oscillator according to claim 1, wherein the lidmember has an conductor insert layer embedded therein.
 9. The oscillatoraccording to claim 1, wherein the lid member is attached to the packagebody by a bonding layer which includes conductive portions at positionscorresponding to the respective lead electrodes, and non-conductiveportions at positions clear of the lead electrodes.
 10. The oscillatoraccording to claim 9, wherein the conductive portions of the bondinglayer are made of a electrically conductive resin, the non-conductiveportions being made of a thermoplastic resin adhesive.
 11. Theoscillator according to claim 9, wherein the conductive portions of thebonding layer are made of a solder paste, the non-conductive portionsbeing made of a thermoplastic resin adhesive.
 12. The oscillatoraccording to claim 9, wherein the bonding layer is entirely made of ananisotropic pressure sensitive conductive elastomer, the bonding layerbeing rendered electrically conductive by predetermined compression onlyat the conductive portions.
 13. The oscillator according to claim 1,wherein the package body comprises a plurality of electrode formingportions made of a metal-platable resin, and a plurality ofnon-electrode forming portions arranged alternately with the electrodeforming portions and made of a non-platable resin, the lead electrodesand the oscillator electrodes being formed on the electrode formingportions of the package body.
 14. A packaged piezoelectric oscillatorcomprising:an insulating package body having a bottom mounting surfaceand a top surface upwardly spaced from the bottom surface, the packagebody further having an upwardly open housing groove which has a bottomsurface formed with oscillator electrodes at both ends of the housinggroove, the package body being externally formed with first to thirdlead electrodes spaced from each other, the first and second leadelectrodes extending upward from the bottom mounting surface of thepackage body and then downward into the housing groove via the topsurface of the package body for electrical connection to the respectiveoscillator electrodes, the third lead electrode extending upward fromthe bottom mounting surface of the package body to the top surfacethereof between the first and second lead electrodes; a piezoelectricelement fixedly received in the housing groove of the insulating packagebody and held in electrically conduction with the respective oscillatorelectrodes; and a lid member upwardly attached to the top surface of thepackage body to close the housing groove, the lid member having a lowerinside surface formed with first to third capacitor electrodes inelectrical conduction with the first to third lead electrodes,respectively, none of the first to third capacitor electrodes extendingonto an upper outside surface of the lid member.